The adult mammalian brain contains self-renewing neural stem cells (NSC) whose progeny divide to produce the three cell types of the brain: neurons, astrocytes, and oligodendrocytes. As the organism ages, both the number of functional NSC and the birth of neurons decline in rodents. A provocative idea is that genes that regulate aging may affect the maintenance of a pool of NSC in adult organisms. An important regulator of aging is the Sirtuin family of NAD+dependent protein deacetylases. One member of this family, Sirt1, has recently been implicated in a wide range of cellular processes, including cell survival and inhibition of differentiation. The overall goal of this project is to determine the role and mechanism of action of Sirt1 in the regulation of the pool of adult mammalian NSC. My preliminary data suggest that Sirt1 is important for NSC self-renewal. Data from our laboratory also suggest that loss of a target of Sirt1, the Foxo family transcription factor Foxo3, diminishes NSC self-renewal. However, the role of Sirt1 in NSC function and the molecular mechanisms of its actions in NSC are not understood. I hypothesize that Sirt1 maintains the population of adult NSC in part by regulating Foxo3. To test this idea, I propose: Aim 1: To determine the importance of Sirt1 in adult NSC self-renewal, proliferation, and survival Aim 2: To dissect the molecular mechanisms of Sirt1 action in adult NSC maintenance I will use a combination of pharmacological, lentivirus-mediated shRNA knockdown, and mouse knockout approaches to assess how Sirt1 loss and gain of function influence self-renewal, proliferation, and survival of adult NSC both in vitro and in vivo during aging. I willl also also test the functional importance of Sirt1/Foxo3 interactions in NSC by co-immunoprecipitation, enzymatic assays, and mutational analysis. Together, these studies will provide a greater understanding of the key molecular players that regulate the pool of adult NSC. PUBLIC HEALTH RELEVANCE: A promising area of biomedical research is the study of adult neural stem cells, which have been implicated in memory formation and brain injury recovery. Characterizing the molecules that impact neural stem cells, such as the 'longevity molecule'Sirt1, may facilitate the development of methods to harness the full regenerative potential of these cells in the context of treating neurodegenerative disease. Importantly, the enzymatic activity of Sirt1 can be targeted with small molecule activators or inhibitors, providing a valuable avenue for therapeutic interventions for neurological disorders that may be treated with neural stem cells.